Compared to single phase, 3 phase AC produces less ripple in the resulting DC waveform when rectified. At the capacitor filtering stage, it is much cleaner with less sag than filtered DC converted from single phase AC.

Are there any benefits to adding a pre-3 phase conversion of single phase AC before converting to DC? If the goal is to achieve the cleanest signal possible, does it perform better or worse than other methods? Finally, are there any power losses in doing so assuming the design uses an established efficient design using 3 single phase transformers connected a 3 phase transformer?

  • 3
    \$\begingroup\$ How would one convert from single phase AC to 3 phase AC? Outside power electronics, I only see a motor-generator. I don't understand using 3 single phase to a 3 phase transformer. \$\endgroup\$
    – greybeard
    Jul 28, 2023 at 5:45
  • \$\begingroup\$ User148.., If you already have 3-phase AC mains... then yes. There are advantages. But if all you have is single phase or North America style split-phase, then no. (There are still relative trade-offs related to full bridge vs just two diodes and a center tap for the full split-phase if you have access to all of L1, L2, and N at once.) \$\endgroup\$ Jul 28, 2023 at 5:55
  • \$\begingroup\$ Can't you can have three separate single phase transformers connected to a single 3 phase transformer? With the right time offset, perhaps with capacitors, you can phase shift two of the single phase transformers. \$\endgroup\$
    – user148298
    Jul 29, 2023 at 2:40
  • \$\begingroup\$ Please put in the question body the "utility" to start from - I readadding a pre-3 phase conversion of single phase AC before… to mean single phase (possibly split). Mains frequency bridge&choke-input filter has been supplanted by "power factor correction" (*voltage proportional*/sinusoidal current shaping?). There are benefits to using 3-phase input beyond available power. \$\endgroup\$
    – greybeard
    Jul 30, 2023 at 10:48

1 Answer 1


You can only convert single phase to three phase AC using an inverter or an rotary converter.
The first one converts to DC first, then back to three phase AC.
The second one powers an electric motor-generator combination.

Costs and losses will be very high. A larger capacitor is almost always cheaper.

Until you're going into kilowatts of DC. Then then it may help you going into a higher frequency or using 12 pulse rectifier with the associated transformer.

  • \$\begingroup\$ See my comment. \$\endgroup\$
    – user148298
    Jul 29, 2023 at 2:41

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.